Flapping foil hydrofoil water craft are known in the prior art. Exemplary of such flapping foil hydrofoil water craft are the devices disclosed in U.S. Pat. No. 7,021,232 and U.S. Pat. No. 6,099,369. These prior art devices are generally characterized by including a foil which moves up and down with an angle of attack of the foil adjusting to maintain propulsion in a forward direction, such that vehicle motion somewhat akin to that of the flukes of a whale tale can be provided. Such flapping foil hydrofoil devices in the prior art also are characterized by including a front foil structure for maintaining balance for the water craft.
These prior art water craft are particularly characterized in a high degree of bobbing up and down as they move over the water. This invention solves such a bobbing problem by utilizing two flapping foils which undergo a heaving (flapping up and down) motion following a sinusoidal pattern, typically 180° out of phase from each other. With this invention, the non trivial problem of optimizing angle of attack for each of the foils throughout their oscillation cycle has also been solved.